This invention relates to a process for assembling a laminated iron core and, more particularly, to a process for assembling a laminated iron core having overlapping joints on a support structure about an electric coil of a shell-type transformer core.
FIGS. 1 and 2 illustrate a typical shell-type electrical transformer to which the present invention can be appplied. In the figure, the transformer comprises a lower tank 1 having a flange 2 at its upper open end. An electrical coil 3 having a coil window 4 is inserted at its bottom in the lower tank 1. The upper portion of the coil 3 projects and is above the lower tank 1. A support beam 5 having an inverted T-shaped cross section is mounted on the lower edge of the window 4 of the coil 3 and on the flange 2 of the lower tank 1. Lower spacers 6 are also mounted on the flange 2.
The transformer further comprises two laminated iron cores 7 disposed on the support beam 5 and the spacers 6 around the legs of the coil 3. A wedge 8 is inserted between the top ends of the iron cores 7 and the upper edge of the window 4 of the coil 3. Upper spacers 9 are disposed between the top ends of the iron cores 7 and core support beams 11 disposed around the coil 3 and mounted to an upper tank 10. The upper tank 10 is attached to the flange 2 of the lower tank 1 by a flange 12.
According to the conventional assembling process, the transformer thus constructed is assembled by first inserting the lower portion of the coil 3 into the lower tank 1 with the coil legs protruding from the lower tank 1. Then, the support beam 5 is placed on the lower edge of the coil window 4 so that the opposite ends are mounted on the flange 2 of the lower tank 1. The spacers 6 are placed on other portion of the flange 2 around the coil 3.
A plurality of laminations or sheets of magnetic material 7a, 7b and 7c are placed and stacked on the spacers 6 and the support beam 5 one by one until the stack reaches a predetermined height to form a substantially rectangular iron core having overlapping joints 7d as shown in FIGS. 1 and 2. During this process, since each of frame-shaped layers of the magnetic sheets is composed of four substantially trapezoidal sections of a magnetic sheet material, four trapezoidal sections must be precisely placed so that the slanted sides abut each other to form the first frame-shaped layer. The second layer is similarly prepared by arranging four trapezoidal sections on the first layer, but with the slanted sides of the trapezoidal sections of the second layer brought into an overlapping relationship with those of the first layer. As is well known this arrangement provides the overlapping joints in which the slanted sides of the sections are staggered by each sheet.
Then, the wedge 8 is inserted between the top lamination of the iron cores and the upper edge of the coil window 4 of the coil 3 and the spacers 9 are provided so that the assembled iron cores 7 are firmly held in their respective positions within the tank by the core support beams 11.
According to the conventional assembling process as above described, each of a large number of the lamination sections are manually precisely positioned one by one with a great care so that the already stacked sections are not dislocated. Also, at each time the stacking of a single layer is finished, the stacked sections must be re-positioned. Therefore, stacking of the lamination sections into a laminated iron core is difficult and time-consuming.